Processing hydrocarbon oils



Patented June 6, 1939 UNITED STATES PATENT OFFICE PROCESSING HYDROOABBONOILS ration of Indiana Application June 25, 1937. Serial No. 150,808

'IClaims.

This invention relates to the process oi converting heavy hydrocarbonoils, including reduced crude oil and gas oil, to lower boiling oils,particularly gasoline. In the cracking oi hydrocarbon oils it hasgenerally been the practice to remove from the crude oil a distillatecharging stock or gas oil which was then subjected to pyrolysis atelevated temperatures to convert a portion of it into gasoline, gas andtar. The high boiling point oi the tar made it possible to eflect aseparation between undesirable coke-forming tarry by-products and theunchanged gas oil which was separated as a distillate in an evaporatortower and iractionator and recycled to the 16 zone of pyrolysis. Whencharging residual stocks to the cracking unit, however, such a sharpseparation cannot be made by distillation between the undesirable tarand the unchanged charging stock, and accordingly considerable unchanged20 cracking stock was lost by being discarded with the undesirable tar.

An object of this invention is to make a clean separation between theunchanged heavy charging stock and the tar produced in the crackingsystem and to recycle the charging stock until its gasoline-producingpotentialities are exhausted. Another object of the invention is tocombine a gas oil cracking operation with a residual oil crackingoperation, discharging both stocks into the same evaporator tower andextracting the combined tar with a liquefied normally gaseoushydrocarbon to produce an ultimate asphalt and a recovered oil which maybe recycled to the cracking zone. Still another object of the inventionis to separate from the recovered oil fraction containedin the tar twofractions of diil'erent average molecular weight, recycling the heavierfraction to the residual oil cracking zone and the lighter fraction tothe gas oil cracking zone.

0 The accompanying drawing, which forms a part of this specification,shows an arrangement 0! three cracking zones, one for reduced crude, and

one-each for light gas oil and heavy gas oil, and extraction apparatusfor separating asphalt from 45 the recycle oil in the tar and forseparating and recycling to different cracking zones, two grades ofrecycle oil.

Referring to the drawing, reduced crude, which, in this example, may bea Mid-Continent reduced 50 crude, is introduced by line ID to heater IIand for this purpose a 40% residual fraction from Mid-Continent crudeoil may be employed. In heater II the oil may suitably be maintainedunder a pressure 0! about 100 to 750 pounds per 55 square inch with anoutlet temperature of about 850-930' F. The hot products are conductedby line I! to evaporator tower II where volatile products are removedand unvaporlzable constituents are withdrawn as a tar through line ll.

Simultaneously, a heavy gas oil fraction having I an A P. I. gravity ofabout 25-30 is introduced by line It into heater l6 where it is suitablyheated to a temperature of about 900-950 F. at any suitable pressure,for example between 200 and 800 pounds per square inch. The hot gas oill0 vapors are conducted by line II to evaporator tower I! where theymingle with the vapors discharged irom heater Ii.

Similarly, a light gas oil which may have an A. P. I. gravity or about30 to 40 is introduced 18 by line Ill into heater is where it issubjected to a high cracking temperature in the range of 925 to 1050 F.,the pressure being suitably maintained between 200 and 800 pounds persquare inch. The light gas oil introduced through line l8 go may containa considerable proportion of heavy naphtha boiling within the gasolineboiling range which it is desired to reform in order to increase itsknock rating. The oil discharged from heater i9 is conducted by line 2|]and soaking drum 2| to evaporator tower H where it is commingled withthe oil and vapors from furnaces ii and I6. Sufllcient soaking volumemay be supplied in the furnace with the elimination of the drum 2|. Thehot vapors from the gas oil furnaces assist an in distilling the productfrom heater I i to produce a clean distillate vapor which is withdrawnfrom evaporator tower It by line 22. Buflicient heat is introduced intoevaporator tower l3 by the three hot oil-vapor streams I have justdescribed to 35 eil'ect a clean separation between the volatilefractions and the non-volatile tarry fractions in tower [3. Thisseparation is assisted by reflux cooling coil 28 or other equivalentmeans or cooling, such as returning a cooled portion or the m distillatefraction to the top of the evaporator tower. At an intermediate point ofthe evaporator tower a heavy gas oil fraction is removed as a sidestream by line 24 and conducted to the inlet of heater it forrecirculation. This stock will have about the same distillationcharacteristics as the fresh 01] charged by line ll, although the A. P.I. gravity will usually be lower. Vapors from evaporator tower II areled by line 22 to bubble tower 2i. Gasoline vapors are conducted fromthe top of said bubble tower to condenser and receiving drum 28 and 21.The condensed liquid fraction separating in bubble tower 25 is withdrawnat the bottom through line 2! by which it is recycled to the inlet ofthe light gas oil cracking furnace. I! desired. reduced crude oil may beintroduced by line 2! into the lower portion of evaporator tower l3, theamount so introduced being regulated to control the temperature andperformance 0! the evaporatortower.

The unvaporized oil or tar withdrawn from evaporator tower II by line His conducted through cooler 30 and thence to extractor 31 where it isbrought into contact at ordinary temperature, for example 70 to 100" R,with a solvent which is introduced by line 32, the tar suitably passingover bailles for this purpose. The extract solution is withdrawn at thetop of the separator through line 33 leading to heater 34 where thetemperature is increased to a point in the vicinity oi the criticaltemperature 0! the solvent. For example, when employing liquid propaneas the solvent the temperature of the extract in heater 34 may suitablybe about 140 to 220 F. In the case where butane is employed as thesolvent the temperature may suitably be raised to about 250 to 315 F.The heated oil is introduced into separator 35 where the increasedtemperature causes a separation of the extracted oil into two fractions,a light oil and a heavy oil, the light oil together with the majorportion of -the solvent being withdrawn from the top of separator 35 byline 36 leading to propane evaporator 31 and the heavier oil fractionbeing withdrawn by line 38 to propane evaporator 39.

The insoluble portion of the tar collecting in the base oi extractor 3|is withdrawn by line Ml leading to evaporator H where propane is removedand the normally solid asphalt which is substantially free from oilfractions is discharged in the heated condition by line 42. Propanewithdrawn from separators 31, 39 and ll is conducted by lines 43 and IIto condenser 45, where the propane vapor is reliquefied under pressureand conducted to propane storage drum 46 whence it is withdrawn by line32 and pump 41 as desired.

The light extract from the base of separator 31, which may have an A. P.I. gravity of about -30, is conducted by line 48 to the inlet of theheavy gas oil heater i6 where it is commingled with the heavy gas oilpreviously described. Thus gas oil which is insufiiciently volatile todlstil into the upper section 01 evaporator tower l3 and to recycle tothe heavy gas oil heater lli as a side stream in line 24 will beconducted to the propane extraction system where it may readily berecovered and returned to the gas oil heater l6 as desired. Likewise,heavy constituents oi: the reduced cmde oil which are charged'into thesystem and escape cracking in the initial pass through the heater II arerecovered in the solvent extraction operation in drum 38, and returnedby line 49 to the cracking system for further conversion into gaso1ine.-As a result of this combination of steps I am enabled to obtain a higheryield of gasoline from a given charging stock and at the same timeobtain a higher knock rating by virtue of the separation o! the stockinto a relatively clean light gas oil fraction which may be cracked at amuch higher temperature to produce a maximum 01' anti-detonatingconstituents. It is preierred'to employ a large amount of reflux inevaporator tower II for the purpose oi knocking back tarry constituentswhich would otherwise be carried through vapor line 22 into bubble towerwhere contamination of the feed to furnace is would result. The heavygas oil fraction withdrawn by line 24, being of higher molecular weightand more readily cracked, is required to be subjected to less severecracking conditions and therefore trouble with coking oi furnace it isavoided. A still lower temperature is used in furnace II, the mainpurpose of which is to viscosity break the reduced crude into productswhich are subsequently cracked in heaters l3 and I8. By my process I amenabled to employ a high reflux ratio in the upper, bellied section ofevaporator l3 without loss oi valuable cracking stock in the tarwithdrawn through line ll, since this stock is subsequently treated withpropane and recovered.

Although I have described my process by speciflc examples thereof, Iintend that my invention be limited only by the following claims.

I claim:

1. The process of converting heavy hydrocarbon oils into motor fuelwhich comprises viscosity breaking a residual oil in a viscositybreaking zone, cracking a gas oil in a gas oil cracking zone,evaporating the hot products oi. said viscosity breaking and gas oilcracking operations, separating gasoline from the vaporized fraction ofsaid products, combining and cooling the unevaporated portions 0! saidproducts, extracting said cooled unevaporated products with a liquefiednormally gaseous hydrocarbon solvent at a temperature substantiallybelow the critical temperature of said solvent, separating theundissolved traction oi. said products from the extract, heating saidextract to a temperature in the vicinity of .the critical temperature ofthe said solvent whereby it is separated into a light recycle oilfraction and a heavy recycle oil fraction, recycling said light recycleoil traction to the said gas oil cracking zone and recycling the saidheavy recycle oil fraction to the viscosity breaking zone.

2. The process of converting heavy hydrocarbon oils into gasoline whichcomprises subjecting a heavy residual oil to viscosity breaking in aviscosity breaking zone, subjecting a heavy gas oil to cracking in aheavy gas oil cracking zone, subjecting a light gas oil to cracking at ahigher temperature in a light gas oil cracking zone, separating theproducts of said cracking operations into a vaporized and an unvaporizedfraction, removing gasoline from said vaporized fraction, cooling saidunvaporized fraction and subjecting it to extraction with a liquefiednormally gaseous hydrocarbon at a temperature substantially below thecritical temperature thereof, separating an insoluble asphaltic fractionfrom the extract, heating the extract to a temperature in the vicinityof the critical temperature oi the said solvent whereby two liquidphases are produced, recovering a relatively light recycle oil from oneof said phases and recycling it to said heavy gas oil cracking zone andrecovering a relatively heavy recycle fraction from the other of saidphases and recycling it to said viscosity breaking zone.

3. The process of claim 2 wherein a distillate fraction boiling abovethe boiling range of gasoline is separated from said vaporized tractionin a fractionating zone and recycled to one oi said gas oil crackingzones.

4. In the process of converting heavy hydrocarbon oils into gasoline ofhigh knock rating wherein a heavy residual incompletely vaporizable oil,a high boiling gas oil and a low boiling gas oil are separately heatedto cracking conditions under pressure, whereby the oils are partiallyconverted into gasoline which is separated from the hot products and theunconverted portions oi the oils are recycled to the crackingoperations, the improvements comprising viscosity breaking the residualoil at a temperature of about 850 to 925 F. and discharging the hotproducts into an evaporating zone, heating said heavy gas oil to atemperature of about 900 to 950 1''. and conducting the hot products tosaid evaporating zone, heating the said light gas oil to a temperatureoi about 925 to 1050' F. and conducting the hot products to saidevaporating zone, separating an unvaporized traction from the vaporizedproducts in said evaporating zo'ne, condensing a portion oi saidvaporized products as heavy reflux condensate therein and in troducingsaid heavy reflux condensate into said heavy gas oil cracking zone,Iractionating said remaining vapors in a tractionating zone to pro ducea gasoline distillate and a reflux condensate, introducing said refluxcondensate into said light gas oil cracking zone, withdrawing andcooling said unvaporized fraction from said evaporating zone andextracting it with a liquefied normally gaseous hydrocarbon solventselected from the class consisting of propane and butane, removingsolvent from the insoluble portion and discarding the high boilinginsoluble portion as a high melting asphalt, conducting the extract to aseparating zone maintained at a higher temperature in the vicinity ofthe critical temperature of the said solvent whereby separation into twophases occurs and separating said extract into a light recycle oil phaseand a heavy recycle oil phase, removing solvent from said light recycleoil phase and introducing the oil into the said heavy gas oil crackingzone, removing propane from said heavy recycle oil phase and introducingthe oil into said viscosity breaking zone.

5. The process of claim 4 wherein solvent removed from said insolublefraction and said light and heavy recycle all phases is condensed andreturned to said extraction zone.

6. The process of claim 4- where in a portion of said heavy residualincompletely vaporizable oil is introduced into said evaporating zonebelow the point of withdrawing said heavy reflux condensate and directlyin contact with hot products from said cracking zones whereby saidportion is preheated and partially evaporated and said hot crackingproducts are quenched, thereby preventing undesirable formation or cokein said evaporating zone.

7. In the process of converting heavy hydrocarbon oils to antiknockmotor fuels wherein a heavy distillate oil and a light distillate oilare subjected to cracking in separate conversion zones and a residualoil is subjected to viscosity breaking in a third conversion heatingzone and the resulting cracked vapors are combined in' an evaporatingzone, the improvement comprising substantially cooling the vaporsreleased in said evaporating zone and condensing therefrom allcoke-forming constituents, subsequently subjecting said vapors tree fromcoke-forming constituents to a fractionating operation and separatingthem into gasoline and a clean distillate recycle stock, charging saidrecycle stock to said light distillate conversion zone and subjecting itto a high conversion temperature between 925 and 10 50 F. whereby amotor fuel of high knock rating is produced, withdrawing from saidevapcrating zone condensate containing coke forming constituents,cooling said condensate and subjecting it to the selective solventaction of a liquefied normally gaseous hydrocarbon whereby heavyhydrocarbons substantially free from cokei'orming constituents areselectively dissolved therein, heating the solution of said heavyhydrocarbons and liquefied gas to a temperature in the vicinity oi thecritical temperature of said gas, whereby said solution is separatedinto a heavy fraction and a light fraction, returning said heavyfraction to said residual oil conversion zone and returning said lighttraction to said MAURICE H. ARVESON.

CERTIFICATE OF CORRECTION.

June 6, 1959.

MAURICE H. ARVESON.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 3,first column, line 32, claim h, for the word "propane" read solvent;and-that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 18th day of July, o. 19 9.

(Seal) Henry Van Arsdale, Acting Commissioner of Patents.

perature of about 850 to 925 F. and discharging the hot products into anevaporating zone, heating said heavy gas oil to a temperature of about900 to 950 1''. and conducting the hot products to said evaporatingzone, heating the said light gas oil to a temperature oi about 925 to1050' F. and conducting the hot products to said evaporating zone,separating an unvaporized traction from the vaporized products in saidevaporating zo'ne, condensing a portion oi said vaporized products asheavy reflux condensate therein and in troducing said heavy refluxcondensate into said heavy gas oil cracking zone, Iractionating saidremaining vapors in a tractionating zone to pro duce a gasolinedistillate and a reflux condensate, introducing said reflux condensateinto said light gas oil cracking zone, withdrawing and cooling saidunvaporized fraction from said evaporating zone and extracting it with aliquefied normally gaseous hydrocarbon solvent selected from the classconsisting of propane and butane, removing solvent from the insolubleportion and discarding the high boiling insoluble portion as a highmelting asphalt, conducting the extract to a separating zone maintainedat a higher temperature in the vicinity of the critical temperature ofthe said solvent whereby separation into two phases occurs andseparating said extract into a light recycle oil phase and a heavyrecycle oil phase, removing solvent from said light recycle oil phaseand introducing the oil into the said heavy gas oil cracking zone,removing propane from said heavy recycle oil phase and introducing theoil into said viscosity breaking zone.

5. The process of claim 4 wherein solvent removed from said insolublefraction and said light and heavy recycle all phases is condensed andreturned to said extraction zone.

6. The process of claim 4- where in a portion of said heavy residualincompletely vaporizable oil is introduced into said evaporating zonebelow the point of withdrawing said heavy reflux condensate and directlyin contact with hot products from said cracking zones whereby saidportion is preheated and partially evaporated and said hot crackingproducts are quenched, thereby preventing undesirable formation or cokein said evaporating zone.

7. In the process of converting heavy hydrocarbon oils to antiknockmotor fuels wherein a heavy distillate oil and a light distillate oilare subjected to cracking in separate conversion zones and a residualoil is subjected to viscosity breaking in a third conversion heatingzone and the resulting cracked vapors are combined in' an evaporatingzone, the improvement comprising substantially cooling the vaporsreleased in said evaporating zone and condensing therefrom allcoke-forming constituents, subsequently subjecting said vapors tree fromcoke-forming constituents to a fractionating operation and separatingthem into gasoline and a clean distillate recycle stock, charging saidrecycle stock to said light distillate conversion zone and subjecting itto a high conversion temperature between 925 and 10 50 F. whereby amotor fuel of high knock rating is produced, withdrawing from saidevapcrating zone condensate containing coke forming constituents,cooling said condensate and subjecting it to the selective solventaction of a liquefied normally gaseous hydrocarbon whereby heavyhydrocarbons substantially free from cokei'orming constituents areselectively dissolved therein, heating the solution of said heavyhydrocarbons and liquefied gas to a temperature in the vicinity oi thecritical temperature of said gas, whereby said solution is separatedinto a heavy fraction and a light fraction, returning said heavyfraction to said residual oil conversion zone and returning said lighttraction to said MAURICE H. ARVESON.

CERTIFICATE OF CORRECTION.

June 6, 1959.

MAURICE H. ARVESON.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 3,first column, line 32, claim h, for the word "propane" read solvent;and-that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 18th day of July, o. 19 9.

(Seal) Henry Van Arsdale, Acting Commissioner of Patents.

